Electro-Absorption Optical Modulator Including Ground Shield

Abstract

A wideband electro-absorption modulating (EAM) device is configured to include a ground shield that functions to minimize the spread of an applied AC voltage beyond the limits of the modulator's electrode. The ground shield includes a grounding electrode disposed in a spaced-apart relationship with the modulator electrode along the ridge of the EAM structure, and a grounding termination used to couple the grounding electrode to a suitable ground location. The ground location may be either on-chip (such as the DC ground of the modulator itself) or off-chip (via an off-chip capacitor, with a wirebond connecting the grounding electrode to the capacitor). The use of a ground shield mitigates the effects that changes in the data rate have on effective length of the modulator as seen by the applied data signal.

Description

TECHNICAL FIELD[0001]The present invention relates to an electro-absorption optical modulator (EAM) typically used in conjunction with a laser structure to create an externally modulated laser (EML) and, more particularly, to the inclusion of a ground shield within the EAM configuration to improve the frequency response of the EAM and extend the operating bandwidth of the EML.BACKGROUND OF THE INVENTION[0002]One type of optical communication system that is particularly well-suited for the transmission of today's high-speed data rate signals is based upon the use of an electro-absorption modulated laser (EML). A continuous wave (CW) optical beam is emitted by a light source and then modulated by an external electrical signal (high frequency) representative of the data to be transmitted. In particular, an electro-absorption modulator (EAM) is positioned to receive both the CW output from the light source and the electrical HF modulation data. The EAM is configured to modulate the CW l...

AI Technical Summary

Benefits of technology

The present invention relates to improving the frequency response of an electro-absorption modulator (EAM) by creating a wideband EAM using a ground shield. The ground shield helps to minimize the spread of the applied AC voltage beyond the limits of the modulator's electrode, which affects the effective length of the modulator as seen by the applied data signal. This invention reduces changes in the data rate on the frequency response of the EAM and allows for a wider range of data to be modulated using the EAM.

Problems solved by technology

One limitation to the performance of an EML is the frequency response of the EAM component.

If the frequency response exhibits a limited 3dB bandwidth, the upper practical limit of the modulation rate of the incoming electrical signal is limited as well, where increases of the modulation rate result in injecting errors in the transmitted optical output data signal.

While problematic for high frequency portions of a data signal stream, low frequency portions, where the data includes a long string of 0's or 1's, may also be impacted by the frequency response of the EAM.

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